1. Field of the Invention
This invention relates to an electromagnetic drive device for a camera performing a focusing action and an exposure effecting action by means of electro-magnetic forces generated by power supplied to the exiciting coils.
2. Description of the Prior Art
Heretofore there have been proposed various kinds of cameras having electromagnetic drive devices. For example, Japanese Laid-Open Patent application No. Sho 50-28832 which was published Mar. 24, 1975 disclosed a technique in which a hollow rotor such as a permanent magnet or the like was around a photo-taking optical path driving diaphragm blades disposed within a lens barrel while a stator consisting of an iron core, an exciting coil, etc. was outside the hollow rotor; and opening and closing actions of the diaphragm blades was controlled by the rotation of this rotor.
There have also been proposed many different arrangements using electromagnetic driving mechanisms for moving a movable lens barrel which carries a photo-taking lens within a stationary tube in the direction of the optical axis of the lens. For example, Japanese Laid-Open Patent application No. Sho 57-20710, published Feb. 3, 1982, disclosed an arrangement in which a stationary tube and a movable lens barrel were provided with a linear motor mechanism. Furthermore, Japanese Laid-Open Patent application No. Sho 56-147132, published Nov. 14, 1981, disclosed a device in which a steped arrangement of magnetic pole teeth was provided on the periphery of a movable lens barrel carrying a photo-taking lens while a stator was on the inner circumference of a stationary tube opposite the electromagnetic teeth to form a stepping motor in conjunction with the latter; and the photo-taking lens was driven by means of pulse waves.
Meanwhile, there have been technological changes in the quality and shapes of sensitive materials such as the use of roll film, discs type film, magnetic tape, magnetic disc, etc. These changes accordingly necessitate changes in photographic apparatus mechanisms. Reduction in size and function consolidation of photographic apparatus have become desirable in response to size reduction i film or tape and to a great extent the adoption of integrated circuits. However, the above-stated electromagnetic drive devices are used for driving diahragm blades and photo-taking lens and they are not incorporated to coordinate the structural arrangement of the photo-taking lens barrels. Therefore, the electromagnetic drive devices have many problems remaining to be solved with respect to their structural arrangement. It is a recent tendency of photographic apparatus to have many different mechanisms incorporated in the body of the apparatus including an automatic focusing mechanism, an automatic film loading mechanism, a winding up mechanism and safety and warning mechanisms. Accordingly, it is desirable to have an apparatus or a mechanism that permits reduction in the number of parts required by coordination and consolidation of different mechanisms and components.